FIG. 1 is a schematic view of a conventional common mode choke coil, and FIG. 2 is an exploded schematic view of the common mode choke coil of FIG. 1. Referring to FIGS. 1 and 2, a conventional common mode choke coil 1 includes magnetic substrates 3 and 10, a composite layer 7, an adhesive layer 8 interposed between the magnetic substrates 3 and 10, and side electrodes 11a, 11b, 11c, 11d for electrically connecting to other components. The composite layer 7 includes insulating layers 6a, 6b and 6c sequentially stacked on the magnetic substrate 3, a coil pattern 4 disposed within the insulating layer 6b, and a coil pattern 5 disposed within the insulating layer 6c. One end of the coil pattern 4 is electrically connected to a conductive wire 12a via a via hole 13a, and the other end of the coil pattern 4 is electrically connected to a conductive wire 12c. One end of the coil pattern 5 is electrically connected to a conductive wire 12b through via holes 13b, 13c, and the other end of the coil pattern 5 is electrically connected to a conductive wire 12d. In addition, the conductive wire 12a is electrically connected to the side electrode 11a, the conductive wire 12b is electrically connected to the side electrode 11b, the conductive wire 12c is electrically connected to the side electrode 11c, and the conductive wire 12d is electrically connected to the side electrode 11d. 
Since the process for manufacturing the side electrodes is complicated and each common mode choke coil 1 needs to be fixed to a fixture during the mass production, the production efficiency of the common mode choke coil 1 is low. In addition, it is more and more difficult to form the side electrodes as the size of the common mode choke coil 1 is becoming smaller and smaller.